In order to meet growing requirements on broadband high-speed mobile access, the Third Generation Partnership Project (3GPP) puts forward a Long-Term Evolution Advance (LTE-Advanced) standard. LTE-Advanced is an evolution of Long-Term Evolution (LTE), keeps a core of LTE, and expands the frequency domain and the time domain on such a basis to fulfil the aims of increasing a spectrum utilization rate, improving system capacity and the like by adopting a series of technologies.
A wireless relay technology is one of technologies for LTE-Advanced, and aims to widen coverage of a cell, reduce dead areas in communication, balance a load, transfer a service of a hotspot and reduce transmitted power of User Equipment (UE). In the wireless relay technology, a Relay Node (RN) provides a function and service similar to those of an ordinary evolved Node B (eNB) for UE accessing the cell of the RN, and further accesses an eNB which serving the RN through a wireless interface like ordinary UE; and here, the eNB serving the RN may be called a Donor eNB (DeNB), and the DeNB is connected with a Mobility Management Entity (MME). As shown in FIG. 1, a DeNB has provided with Serving GateWay (S-GW) and Packet Data Network GateWay (P-GW) functions, and also has a relay GateWay (GW) function. When an RN accesses a DeNB, an MME may select a local S-GW and P-GW located in the DeNB for the RN, wherein the S-GW is responsible for data information transmission, forwarding, routing and the like between the DeNB and the P-GW as well as caching of a downlink data packet; and the P-GW is an anchor point of data bearer, and is responsible for data packet forwarding, analysis, legal monitoring and service-based charging and Quality of Service (QoS) control. A relay GW has an S1/X2 proxy function, and is responsible for processing related S1/X2 signalling of UE, distinguishing signalling of different UE and performing correct message processing. For example, there are multiple RN like RN1 in a fixed relay scenario, and the X2 proxy function is defined as follows: there is an X2 interface between a DeNB and RN1, there are also X2 interfaces between the DeNB and adjacent eNBs around or other RNs, and when the DeNB with a relay GW function receives an X2 message from RN1, the DeNB may determine the adjacent eNBs or RNs to which related X2 information is to be transmitted according to cell information in the X2 message; here, if the received X2 message contains a UE application layer protocol identifier, the DeNB allocates a new UE application layer protocol identifier to UE or replaces the UE application layer protocol identifier in the message with a UE application layer protocol identifier which has been allocated to the UE, and contains the new UE application layer protocol identifier in the X2 message sent to the other adjacent eNBs as the UE application layer protocol identifier allocated by the DeNB; correspondingly, when the DeNB with the relay GW function receives an X2 message from another eNB or another RN except RN1, the DeNB may determine whether to send the related X2 message to RN1 or not according to the cell information in the X2 message; and here, if the received X2 message contains the UE application layer protocol identifier, the DeNB allocates the new UE application layer protocol identifier to the UE or replaces the UE application layer protocol identifier contained in the message, and includes the new UE application layer protocol identifier into the X2 message sent to RN1 as the UE application layer protocol identifier allocated by the DeNB. For example, if the received X2 message indicates that RN1 is a target cell, the corresponding X2 message is sent to RN1. For example, if the received X2 message is an eNB configuration updating message, the eNB configuration updating message may further be sent to RN1. In such an X2 proxy manner, information transmission between an RN and another adjacent eNB or RN is implemented; wherein, S1/X2 signalling between the RN and the DeNB with the relay GW function is wirelessly born by the RN, and is routed and forwarded for transmission through an RN SGW/PGW.
Along with the large-scale construction and commissioning of high-speed railways, requirements on communication on trains continuously increase. A practical speed of a high-speed railway has reached 350 kilometers per hour at present, and it is difficult to meet a communication quality requirement of the high-speed railway by coverage of an existing network eNB under the influence of Doppler frequency shift, frequent cell handover, great penetration loss of a carriage of the high-speed railway and the like. Therefore, deployment of a relay node, called a Mobile Relay (MR), on the high-speed railway is put forward in the industry. FIG. 2 is a diagram of a deployment scenario of an MR, and as shown in FIG. 2, users such as UE1 and UE2 on a high-speed train directly communicate with a relatively still MR, and the MR may be switched between different DeNBs in a movement of the high-speed train, to avoid simultaneous handover of a great number of users in a carriage of the high-speed train, and ensure quality of communication between the UE and the MR. In addition, enhancing a backbone connection between the MR and the DeNB can better solve the abovementioned problem of the high-speed railway.
For an MR scenario, there have proposed multiple architectures at present, wherein in an architecture of an Alt2 reusing fixed scenario without relocation, i.e. an architecture where a DeNB has been provided with S-GW, P-GW and relay GW functions, when an MR accesses an initial DeNB, an X2 proxy manner may be reused for implementing X2 message transmission between the MR and another eNB. However, in such an architecture, along with the movement of the train, after the MR goes far away from the initial DeNB and is switched to another DeNB, a relay GW, RN and PGW of the MR may still reside in the initial DeNB, and because the initial DeNB is far away from a current position of the MR and there may not be any X2 interface between the initial DeNB and an adjacent eNB of the MR, an X2 proxy function of the initial DeNB may not be realized between the MR and the eNB under such a condition, which may cause influence on the X2 message transmission between the MR and the other eNB and further reduce user experiences.
In a Home evolved Node B (HeNB) scenario, when a HeNB performs information interaction with an adjacent eNB or HeNB through an X2 proxy, similar problems may appear, which causes influence on X2 message transmission between the HeNB and another eNB or HeNB. In the HeNB scenario, the X2 proxy may also be called an X2 GW, and has a function similar to that in the MR scenario.